The Transgenic Core works with Investigators to generate animal models what will increase our understanding of cancer and the function of genes in involved in cancer. This Core was established in 1989 and produces transgenic mice and rats, and gene-targeted mice (knockouts) for Cancer Center members. The Transgenic Core maintains specialized equipment for micromanipulation, mouse embryonic stem (ES) cell culture, embryo cryopreservation, bacterial artificial chromosome (BAC) recombineering. This collaborative Core combines the expertise of Center members in the molecular biology of Important genes with the Core's expertise in producing genetically engineered mice, Unique capabilities that set this Transgenic Core apart are 1) guaranteed production of transgenic mice and rats. 2) routine production of BAC transgenic mice, 3) production of transgenic mice In unique genetic backgrounds, 4) gene targeting In C57BL/6 ES cell lines in addition to 129/Sv ES cells, 5) de novo derivation of mouse ES cell lines, 6) genetic modification of BACs, 7) open access to reagents and equipment, and 8) training in ES cell culture and micromanipulation. Access to the Transgenic Core eliminates the need for Investigators to purchase specialized equipment and train personnel in embryo micromanipulation, ES cell culture, and BAG recomblneering. Consultation on all aspects of transgenic and ES cell research is provided, from the design of transgenes and conditional targeting vectors to mouse breeding and phenotype analysis. We deliver an average of nine transgenic founder mice and guarantee that at least three founders will be produced for each DNA construct submitted to the Core, The Core electroporates totipotent ES cells with targeting vectors, selects 480 ES cell clones, and provides Investigators with ES cell DNA to screen for homologous recombination with targeting vectors. We guarantee that ES cell clones with desired genetic changes will be microinjected Into at least 60 mouse blastocysts to produce ES cell-mouse chimeras. The efficiency of these procedures meets or exceeds published values in the literature. A full suite of assisted reproductive technologies is offered; mouse cryopreservation, mouse In vitro fertilization, sperm cryopreservation, recovery of mice from cryopreserved embryos or sperm. Center members have taken advantage of these capabilities to establish develop models of gastric cancer, pancreatic cancer, skin cancer, colon cancer, prostate cancer, breast cancer, and medulioblastoma.